1. Field of the Invention
The present invention relates to drive technology for light emitting elements such as a light emitting diode (referred to below as LED) or an organic EL element, and in particular to drive technology by AC voltage.
2. Description of the Related Art
In recent years, light emitting elements such as LEDs of high luminous efficiency and the like have been attracting attention as light sources instead of conventional lighting. For example, attempts are being made to use light emitting elements such as LEDs as lighting in place of fluorescent tubes, and as lighting in vehicle headlights and the like.
In this way, with the spread of LED application, in consideration, for example, of usage of LEDs as substitutes for fluorescent tubes and the like, it is desirable to be able to drive light emitting elements directly, using an AC voltage such as a 100 V commercial power supply or the like. Technology for driving an LED by an AC voltage is disclosed, for example, in Patent Documents 1 and 2.
Patent Document 1: Japanese Patent Application, Laid Open No. H8-148721
Patent Document 2: International Publication No. WO2003/056878
In cases in which a light emitting element such as an LED is driven by an AC voltage, when a large current exceeding the rating flows in the light emitting element, there is a risk of having an effect on reliability of a circuit. Furthermore, it is desirable that brightness of the light emitting element be maintained at a constant value even if amplitude of the AC voltage varies.